[geocentrism] Re: Geosynchronous/Geostationary satellites
- From: "Neil Robertson" <nroberts@xxxxxxxxxxxxxxxxxx>
- To: <geocentrism@xxxxxxxxxxxxx>
- Date: Mon, 25 Oct 2004 03:02:54 +1000
Gary,
> Neil,
>
> Thank you very much for this remarkably clear explanation of the satellite
> situation. It helped greatly. I was under the misconception that these
> satellites' orbits would be parallel with the equator, not at an angle to
> it. I have two questions.
Glad I could help out. You have however misunderstood my explanation to some
degree.
To have a satellite appear stationary it must orbit above and parrallel to
the equator but that is the ideal situation and some variations occur. My
explanation tried to cover all the aspects of satellite orbits that would
effect the perceived path of the satellite and to give you a clear
explanation of where ToSeeks figure of eight comment was coming from.
> According to ToSeek, all geosynchronous satellites performed figure
> eights.
> If that is true, then do all these geosynchronous satellites have an orbit
> so inclined to the equator? Are there none that orbit parallel with the
> equator?
They try to place the satellite in an orbit parallel to the equator, in a
circular orbit and at zero inclination. The point is that this orbit is not
100% stable due to variations in the earths gravity (caused by density
variations in the earth) which has a tendancy to push the orbit elliptical,
and the force applied by the moons gravity which tends to increase the
orbital inclination towards that of the Moon about the earth. The end result
of this is that figure of eight path that has been mentioned before. Bear in
mind this drift is gradual and slight but accumulates over time.To ensure
that the satellite is still directing its communication equipment in the
footprint on earth required, the satellite controllers fire small attitude
adjusting jets periodically to correct the drift.
There is only so much fuel on board the satellite to correct the drift and
when this runs out the satellite is useless and they have to launch another.
The usual course of action by the controllers, when the fuel on the craft is
nearly expended, is to fire the jets and place the satellite in a graveyard
orbit some 500-1000 km above its operational orbit so the eventual drift of
the satellite will not interfer with other satellites in Geostationary
orbits. Its awful crowded up there.
> Second question. What powers these satellites? Why are some elliptical,
> others circular? What force determines this aspect? If we always compare
> these satellites to the moon, and Kepler is any authority, why is there
> variance here?
The satellites are equiped with solar cells for power and batteries as
backup. This is to power the electronics of the satellite only. The satelite
requires no power to complete its orbit and will orbit indefinately unless
some external force is applied to it. The satellite does as I have mentioned
previously have small correcting jets to adjust for drift in its orbit but
that is all.
I have seen you ask this question before and it appears that you do not
understand the logistics of getting the satellite into orbit and what this
actually means so I will give you a brief explanation.
The ideal situation would be to launch the satelite from the equator as that
would give it the greatest boost from the earths rotation and you would not
have to worry about any inclination with respect to the equator.
Unfortunately I don't think there are any launch sites on the equator and
most satellites are launched from the northern hemisphere.
Take for example the Kennedy space centre launch facility. This is located
28 degrees 36 minutes north latitude.The earths rotation speed at this
latitude is some 1440 kph and the rocket sitting on the launch tower is also
travelling at this speed relative to space. The rocket itself is a
multistaged affair(3 or 4) and is fired initially straight up so that it
will get through the thickest part of the atmosphere as quickly as possible
to minimise fuel use. At a height of approximately 200 km the guidance
system alters the angle of accent to bear east in line with the earths
rotation. The various stages fire in sequence driving the craft till it
reaches a point some 36000 km above the earth. At this point the orbit is
elliptical and to get the satellite to its final orbit the final stage
rockets are fired at the farthest point in its orbit and in the direction it
is travelling. The end result of this is to make the orbit circular.
The satellite is now going around 7000 kph and if the earth wasn't there it
would head into space in a straight line. Because of the earths gravity the
satellite falls towards the earth and because the satellite has a forward
velocity it misses the earth and is in a continual free fall. The result is
a perpetual orbit around the earth and no power is required for the
satellite to continue in this manner indefinately.
I should also point out that at some point in the rockets trajectory it is
angled such that the inclination caused by its launch from a spot other than
the equator is accounted for and the satellite ends up at zero inclination
to the equator.
Whether a satellites orbit is circular or elliptical inclined or at zero
inclination is purely at the whim of the guys that launch the craft. They
merely make the necesary adjustments to the angle of the launch and the
duration of the rocket burn. All mathematics and Newtons Laws basically.
As far as the moon Kepler etc, the moons orbit is elliptical as is most of
the planets and moons in the solar system, and satellites act in the same
manner as other orbiting bodies.. You could look at the fact that a circle
is a pure form, perfect you might say but in terms of the solar system there
are many irregularites. The planets moons etc are not perfect spheres or of
uniform density so cicular orbits are not the logical outcome.
> Last question, do you see a geocentric explanation for the movement you
> describe of these satellites?
No.
Regards ,
Neil.
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